Solid state/class d vs tube amps

[DavesnothereCA]

J Darr wrote a book on troubleshooting tube amps. Most of the book is available on the web.

You can find most schematics on the web also.

~
I am truly amazed at how many schematics and owner's manuals of pre-Internet equipment have been scanned in and posted on the web !

Tube amps, I had most of the classic schematics archived on old photocopies, somewhere, but it is still easier to consult Professor DuckDuckGo to access someone else's capture than to actually FIND mine, as I do not need them all that often these days and had lost track of them some time ago.

Earlier this year, when I decided to bring my old Acoustic 150 head back from about 2 decades of storage, I encountered an audio hum which was most likely preamp filter caps dried out.

And yes, while I could have flown blind on that particular one, the schematic was out there, easy to find and download.

I installed replacements which had both a higher capacitance and voltage rating, wiped the jack contacts and sprayed the pots, snugged the power transistor screws a bit, and all was again fine.

My active EMGs matched the amp's less sensitive input, and I patched in a tiny TC Electronic 2-band portable parametric for more tone variance, as the 150 only has bass and treble shelving, unlike the fancier and more powerful Acoustic 370 and 470 heads which I had owned at various times in the past.

And I really ought to change the 150 over to a grounded power cord, but the old ground switch still works.
~

 

[BadExample]

No, I'm Dave!

 

[Eddie LeBlanc]

~
Tube amps are not harder to make.

I built and repaired tube amps before I was even a musician, and still could do so today if required, as their circuitry has not evolved as much as that of s/s amps has.

The vast majority of what I learned about them during the 60s and 70s can still be applied today.

OTOH, tube amps cost more to make for two main reasons :

(1) Tube amps must include components not required in solid state amps, such as an output transformer, and they need a larger power transformer than s/s amps, to heat the tube filaments (and also because tube amps run power stages which generally are less efficient than some of the newer solid state amps such as Class 'D' models).

That has always been the case, and the 2nd reason is one which has become more true as more time has passed.

(2) As less tube amps are being made these days, makers cannot economize as much from the scale of mass production, whereas makers of s/s amps more often can.

And the price of higher quality components, like 1% Metal film resistors, and extreme quality poly caps, that handle those voltages have sky rocketed, if you can even find them. So a quality Tube Amp is real expensive for sure. Especially if you want one that doesn't have cheap Carbon Resistors, and crappy Caps. That is why a McIntosh 275 amp (dual channel 75 watt quad KT88s) sells for over $6K new.

It could be said that it is harder to build a tube amp which costs less than a certain amount of money, but they are not harder to build from a technical viewpoint.
~

 

[somebrains]

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Yes, tube amps do have higher voltages inside, and require due care while testing and repairing.

That doesn't negate what I said earlier though.
~

Ok, so you wanna give me a hand with this head bc it's just going to collect dust at the local tech's shop if I don't do something about it.

Everyone else local is full up and not taking new customers.

I'm about ready to take it down to LA on my next work trip and see if any TB members have space in line.

 

[agedhorse]

Ok, so you wanna give me a hand with this head bc it's just going to collect dust at the local tech's shop if I don't do something about it.

Everyone else local is full up and not taking new customers.

I'm about ready to take it down to LA on my next work trip and see if any TB members have space in line.

Any shop that can't turn gear around in a couple of weeks is not a real shop, period. None of this stuff is rocket science for a real, well qualified tech. What we are now seeing is the result oft he real techs migrating out of the industry and being replaced by hobbyists and hacks that do not have the troubleshooting knowledge and skill to get the work done efficiently and properly the first time.

I ran a shop many years ago and had no problem turning gear around in a week, and I know other techs with similar abilities. Currently with Genz Benz gear that I continue to support for the large corporations that owned the brand before discontinuing it, EVERY repair gets turned around in 48 hours. Even Mesa, with all the very old legacy amps turns repairs around in a few weeks (unless there's some custom fabrication that is needed) and there are many tens of thousands of these amps out in the wild.

My advice to anybody who wants to make a living in this industry servicing gear... learn exactly how it works, learn the theory, learn solid troubleshooting techniques, and learn how to run a business as a business. The rest is easy

 

[-Asdfgh-]

Any shop that can't turn gear around in a couple of weeks is not a real shop, period. None of this stuff is rocket science for a real, well qualified tech. What we are now seeing is the result oft he real techs migrating out of the industry and being replaced by hobbyists and hacks that do not have the troubleshooting knowledge and skill to get the work done efficiently and properly the first time.

I ran a shop many years ago and had no problem turning gear around in a week, and I know other techs with similar abilities. Currently with Genz Benz gear that I continue to support for the large corporations that owned the brand before discontinuing it, EVERY repair gets turned around in 48 hours. Even Mesa, with all the very old legacy amps turns repairs around in a few weeks (unless there's some custom fabrication that is needed) and there are many tens of thousands of these amps out in the wild.

My advice to anybody who wants to make a living in this industry servicing gear... learn exactly how it works, learn the theory, learn solid troubleshooting techniques, and learn how to run a business as a business. The rest is easy

One fly in the ointment we have where I work (which is nothing to do with amps), sometimes, is delays on components that need to be shipped from manufacturers on the other side of the world. Or sometimes closer when the remnants of hurricanes come through, or volcanoes explode. I don't think we have specific volcano insurance.

 

[agedhorse]

One fly in the ointment we have where I work (which is nothing to do with amps), sometimes, is delays on components that need to be shipped from manufacturers on the other side of the world. Or sometimes closer when the remnants of hurricanes come through, or volcanoes explode. I don't think we have specific volcano insurance.

Maybe, but this is more the exception to the rule. It's like the tech whose mother dies 3 or 4 times a year to justify delays

 

[somebrains]

One fly in the ointment we have where I work (which is nothing to do with amps), sometimes, is delays on components that need to be shipped from manufacturers on the other side of the world. Or sometimes closer when the remnants of hurricanes come through, or volcanoes explode. I don't think we have specific volcano insurance.

A lot of us bring applicable parts kits in, otherwise it turns into a time suck.
Sad, bc most of us have worked in stores and the common skillgap is amps.
We have heard the excuses, maybe used them, but at some point it goes past where you can let the BS go and you look for other options.

 

[-Asdfgh-]

Maybe, but this is more the exception to the rule. It's like the tech whose mother dies 3 or 4 times a year to justify delays

Ah... some people have lots of mothers, you know

 

[DavesnothereCA]

I said earlier :
~
"Tube amps are not harder to make.

I built and repaired tube amps before I was even a musician, and still could do so today if required, as their circuitry has not evolved as much as that of s/s amps has.

The vast majority of what I learned about them during the 60s and 70s can still be applied today.

OTOH, tube amps cost more to make for two main reasons :

(1) Tube amps must include components not required in solid state amps, such as an output transformer, and they need a larger power transformer than s/s amps, to heat the tube filaments (and also because tube amps run power stages which generally are less efficient than some of the newer solid state amps such as Class 'D' models).

That has always been the case...."
~

And the price of higher quality components, like 1% Metal film resistors, and extreme quality poly caps, that handle those voltages have sky rocketed, if you can even find them. So a quality Tube Amp is real expensive for sure. Especially if you want one that doesn't have cheap Carbon Resistors, and crappy Caps. That is why a McIntosh 275 amp (dual channel 75 watt quad KT88s) sells for over $6K new.

~
I would LOVE to see 1% resistors in ANY amplifier, tube or s/s, and better caps too.

But back in the day, the best resistors we got in mainstream amp brands were 5%, and more commonly 10%.

Caps were older designations too.

The amps still worked.

That's why I did not mention resistors and caps in my earlier post which you quoted.

But even if we used the same grades of R & C parts now as back then, today's tube amps will still cost more to build, for the reasons which I mentioned earlier (and brands like McIntosh being a notable exception, as they always used better parts).

And not all brands of today's s/s amps use the better grades of parts which you described, do they ?

If they did, some of the less expensive makes would have to jack their prices somewhat, I reckon.

= = =

BTW, I should add a THIRD reason that tube amps tend to cost more these days.

(3) Folks who CHOOSE to buy tube amps today are generally willing to spend more money for them on average, compared to people who now buy solid state amps of ANY class of output stage, so today's tube amp makers feel that they can AFFORD to build a better grade of amp for those customers.

 

[DavesnothereCA]

Ok, so you wanna give me a hand with this head bc it's just going to collect dust at the local tech's shop if I don't do something about it.

Everyone else local is full up and not taking new customers.

I'm about ready to take it down to LA on my next work trip, and see if any TB members have space in line.

~
That would likely be more economical than shipping it to me in Canada (and back), regardless of what make and model it is, nor what its problem is, and much as I appreciate you trusting me enough to ask.
~

 

[agedhorse]

Why 1% resistors? A good designer will make their designs robust enough not to have to rely on such parts.

A good designer will design their products so they do not depend on parts like this, because some drift can occur over time, ageing and such and this should not affect the tone or stability of the amp.

There are exceptions, but not many places where 5% won't deliver essentially identical performance.

 

[somebrains]

~
That would likely be more economical than shipping it to me in Canada (and back), regardless of what make and model it is, nor what its problem is, and much as I appreciate you trusting me enough to ask.
~

My bad, CA means California to me.
Figured you were somewhere near where I'd work.

Oh well, the search continues.

We had a good amp guy in San Anselmo, it just never occurred to anyone to learn from him.
The guy he took on late is this dbag we kept seeing work his way into all sorts of trades.
He is a continual learner, never a doer.

Guess he is locked into the whole apprentice deal and never becoming a Jedi.

 

[byacey]

Of course, but it can also give a false sense of confidence that can be very dangerous. IIRC, there wasn't all that much on safety in his book... actually it's on my bookshelf (1977 ed) so I did check on this and the safety stuff is horrible, absolutely insufficient for somebody who is trying to learn.

Shock from the plate supply is a fast teacher, a lesson not soon, if ever, forgotten.

 

[GreyBeard]

Maybe, but this is more the exception to the rule. It's like the tech whose mother dies 3 or 4 times a year to justify delays

Used to have a KB player who used that excuse for not showing up for setup.

 

[agedhorse]

Shock from the plate supply is a fast teacher, a lesson not soon, if ever, forgotten.

On the PS-400, it might be a trip to the ER (if you survive the amp falling on you after you land on the floor yourself).

 

[byacey]

On the PS-400, it might be a trip to the ER (if you survive the amp falling on you after you land on the floor yourself).

That would be just adding insult to injury!

 

[agedhorse]

That would be just adding insult to injury!

Yup. I learned this lesson very early on in my career, I had recently taken over a service shop that had been run by Nelson Pass (we both went to the same university) and I was working on a big tube power amp and got bit bad, didn't see a strand of wire. I went over backwards, fortunately the amp stayed on the bench, but I almost landed on another amp that was behind my stool against some steel shelving. That would have been worse than the shock by far. I hurt for a couple of days from those involuntary gymnastics.

 

[byacey]

Yup. I learned this lesson very early on in my career, I had recently taken over a service shop that had been run by Nelson Pass (we both went to the same university) and I was working on a big tube power amp and got bit bad, didn't see a strand of wire. I went over backwards, fortunately the amp stayed on the bench, but I almost landed on another amp that was behind my stool against some steel shelving. That would have been worse than the shock by far. I hurt for a couple of days from those involuntary gymnastics.

I think much of the post trauma pain comes from your muscles being violently tensed from the current. Most good techs only experience this once in their career. After the first time shock, they are much more mindful in the future of where the high voltage is, and where they stick their fingers.

 

[somebrains]

Yup. I learned this lesson very early on in my career, I had recently taken over a service shop that had been run by Nelson Pass (we both went to the same university) and I was working on a big tube power amp and got bit bad, didn't see a strand of wire. I went over backwards, fortunately the amp stayed on the bench, but I almost landed on another amp that was behind my stool against some steel shelving. That would have been worse than the shock by far. I hurt for a couple of days from those involuntary gymnastics.

...and that's why no one I knew wanted to become an amp tech.
I had an uncle that was a union iron worker, he had a buddy that was a PG&E lineman.
No one wanted to do those jobs either bc they involve a significant chance of spine injury and waking up at 4am.

Some things you do bc you love it, or feel responsibility to keep a tradition alive.